Spoke to a surveyor, they think my suspicion is correct, so will fill the void with some rock wool spare from the loft. (would prefer rock wool matt, but silly to buy 8m2 of it when I need 0.5m2). then run a dehumidifier for a bit to dry it out.
We have an area of wall just above the skirting board about 40 cm long that is damp to touch and has peeling wallpaper. It's adjacent to a conservatory separated from the house by a bifold door. So I opened up a hole in the plaster board to check the cavity. Our 1930s house has foam cavity insulatio...
